Using a graphing calculator to check simplification problems
description
Transcript of Using a graphing calculator to check simplification problems
USING A GRAPHING CALCULATOR TO CHECK
SIMPLIFICATION PROBLEMS
You can always check your answer to a simplification problem using your calculator (or you can use another method that will be shown here). This example is taken from the January 2010 Math B Regents (number 13)
22 yxxy
This example is taken from the January 2010 Math B Regents (number 13)Which of the following is equivalent to
A B C D
yx 1
yx 1
yx 1
yx 1
Without a calculatorChoose a value for x and y. Let’s say x = 2 and y = 1Now check the value you get when you substitute these values of x and y in the original expression and see what value you get
22 yxxy
22 1221
141
31
31
Now check each answer for x = 2 and y = 1 and see if you get -1/3
A
B
C
D
yx 1 1
11
121
111
121
yx
1
yx 1
31
121
yx 1
31
31
121
This is the only one that has the same value as our original expression
Using the graphing calculator to do this
You can store values for variables into your calculator. First we’ll store x = 2
Press the following sequence: 2, STO, XYour screen should show this Press enter:
Now our calculator has x set equal to 2
We will do the same for y: we will store 1 into yThe sequence we will press is: 1, STO, APLHA, 1
Your screen should show this:
Press enter:
Now check the value of the original expression using our values
22 yxxy
The sequence of keys we will press:Left parenthesis, ALPHA, 1, - (minus not negative), X, Right parenthesis, division symbol, left parenthesis, X, x^2 button, - (minus not negative), ALPHA, 1, x^2 button, ENTER
After entering this sequence of buttons, this is what you should see on your screen:
The next half:Here’s what you should have on your screen
Pressing enter you should get:
If you want to convert your decimal to a fraction, press the following sequence:
MATH, 1 Here’s what you’ll see on your screen
Press ENTER
Check the other expressions in a similar manner. The only answer that matches will be D.
Be carefulYou must be careful about the values you choose for x and y
For example in our last example22 yxxy
We could not let x = y since that would cause division by 0 which is illegal.
You should only use this as a checking tool, NOT as your primary method of simplifying.